sys/vtimer: spin on short duration in vtimer_sleep
sys/vtimer: spin on short duration in vtimer_sleep

closes #571

abkam07/RIOT,x3ro/RIOT,patkan/RIOT,asanka-code/RIOT,x3ro/RIOT,immesys/RiSyn,1blankz7/RIOT,backenklee/RIOT,Darredevil/RIOT,l3nko/RIOT,toonst/RIOT,altairpearl/RIOT,biboc/RIOT,rfswarm2/RIOT,sgso/RIOT,Lexandro92/RIOT-CoAP,changbiao/RIOT,OlegHahm/RIOT,alignan/RIOT,Josar/RIOT,herrfz/RIOT,roberthartung/RIOT,abp719/RIOT,shady33/RIOT,rfswarm/RIOT,wentaoshang/RIOT,rousselk/RIOT,locicontrols/RIOT,gbarnett/RIOT,yogo1212/RIOT,MohmadAyman/RIOT,A-Paul/RIOT,neumodisch/RIOT,luciotorre/RIOT,jhollister/RIOT,mtausig/RIOT,yogo1212/RIOT,lazytech-org/RIOT,MonsterCode8000/RIOT,malosek/RIOT,FrancescoErmini/RIOT,chris-wood/RIOT,syin2/RIOT,avmelnikoff/RIOT,koenning/RIOT,dailab/RIOT,jremmert-phytec-iot/RIOT,rakendrathapa/RIOT,altairpearl/RIOT,tfar/RIOT,ThanhVic/RIOT,luciotorre/RIOT,beurdouche/RIOT,centurysys/RIOT,alignan/RIOT,brettswann/RIOT,roberthartung/RIOT,thiagohd/RIOT,patkan/RIOT,bartfaizoltan/RIOT,ant9000/RIOT,EmuxEvans/RIOT,automote/RIOT,adrianghc/RIOT,daniel-k/RIOT,kushalsingh007/RIOT,openkosmosorg/RIOT,immesys/RiSyn,abkam07/RIOT,attdona/RIOT,syin2/RIOT,smlng/RIOT,jremmert-phytec-iot/RIOT,dhruvvyas90/RIOT,ros2/ros2_embedded_riot,thiagohd/RIOT,adrianghc/RIOT,LudwigOrtmann/RIOT,abkam07/RIOT,LudwigKnuepfer/RIOT,d00616/RIOT,josephnoir/RIOT,chris-wood/RIOT,Osblouf/RIOT,rfswarm2/RIOT,MarkXYang/RIOT,JensErdmann/RIOT,x3ro/RIOT,rfswarm2/RIOT,basilfx/RIOT,arvindpdmn/RIOT,DipSwitch/RIOT,OlegHahm/RIOT,shady33/RIOT,LudwigOrtmann/RIOT,rakendrathapa/RIOT,gautric/RIOT,PSHIVANI/Riot-Code,biboc/RIOT,ks156/RIOT,syin2/RIOT,gebart/RIOT,fnack/RIOT,AnonMall/RIOT,changbiao/RIOT,marcosalm/RIOT,alignan/RIOT,MohmadAyman/RIOT,bartfaizoltan/RIOT,herrfz/RIOT,kerneltask/RIOT,rfswarm/RIOT,dhruvvyas90/RIOT,Darredevil/RIOT,ros2/ros2_embedded_riot,daniel-k/RIOT,emmanuelsearch/RIOT,koenning/RIOT,binarylemon/RIOT,lebrush/RIOT,aeneby/RIOT,TobiasFredersdorf/RIOT,adjih/RIOT,tdautc19841202/RIOT,gautric/RIOT,koenning/RIOT,sgso/RIOT,basilfx/RIOT,l3nko/RIOT,mtausig/RIOT,attdona/RIOT,dhruvvyas90/RIOT,phiros/RIOT,AnonMall/RIOT,nsol-nmsu/RIOT,binarylemon/RIOT,mziegert/RIOT,jbeyerstedt/RIOT-OTA-update,msolters/RIOT,lebrush/RIOT,1blankz7/RIOT,jfischer-phytec-iot/RIOT,authmillenon/RIOT,abp719/RIOT,neiljay/RIOT,ks156/RIOT,arvindpdmn/RIOT,OTAkeys/RIOT,alex1818/RIOT,d00616/RIOT,ant9000/RIOT,MarkXYang/RIOT,DipSwitch/RIOT,rfswarm2/RIOT,alex1818/RIOT,wentaoshang/RIOT,wentaoshang/RIOT,Osblouf/RIOT,jasonatran/RIOT,Hyungsin/RIOT-OS,abkam07/RIOT,1blankz7/RIOT,kbumsik/RIOT,Lexandro92/RIOT-CoAP,Osblouf/RIOT,toonst/RIOT,gbarnett/RIOT,thiagohd/RIOT,adrianghc/RIOT,Osblouf/RIOT,jferreir/RIOT,Osblouf/RIOT,bartfaizoltan/RIOT,rfswarm/RIOT,luciotorre/RIOT,ros2/ros2_embedded_riot,malosek/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,smlng/RIOT,zhuoshuguo/RIOT,arvindpdmn/RIOT,gautric/RIOT,abkam07/RIOT,kushalsingh007/RIOT,ks156/RIOT,shady33/RIOT,smlng/RIOT,EmuxEvans/RIOT,rfswarm/RIOT,malosek/RIOT,sumanpanchal/RIOT,EmuxEvans/RIOT,gebart/RIOT,1blankz7/RIOT,mtausig/RIOT,jfischer-phytec-iot/RIOT,alex1818/RIOT,thomaseichinger/RIOT,altairpearl/RIOT,BytesGalore/PetersRIOT,avmelnikoff/RIOT,Lotterleben/RIOT,thiagohd/RIOT,msolters/RIOT,aeneby/RIOT,BytesGalore/PetersRIOT,alex1818/RIOT,daniel-k/RIOT,dailab/RIOT,emmanuelsearch/RIOT,bartfaizoltan/RIOT,OTAkeys/RIOT,sgso/RIOT,d00616/RIOT,lebrush/RIOT,FrancescoErmini/RIOT,rakendrathapa/RIOT,altairpearl/RIOT,LudwigKnuepfer/RIOT,Darredevil/RIOT,asanka-code/RIOT,haoyangyu/RIOT,nsol-nmsu/RIOT,jfischer-phytec-iot/RIOT,marcosalm/RIOT,katezilla/RIOT,locicontrols/RIOT,aeneby/RIOT,kYc0o/RIOT,robixnai/RIOT,kaleb-himes/RIOT,miri64/RIOT,ntrtrung/RIOT,centurysys/RIOT,centurysys/RIOT,rakendrathapa/RIOT,zhuoshuguo/RIOT,benoit-canet/RIOT,plushvoxel/RIOT,kb2ma/RIOT,jferreir/RIOT,dkm/RIOT,Yonezawa-T2/RIOT,dkm/RIOT,changbiao/RIOT,gbarnett/RIOT,immesys/RiSyn,kaleb-himes/RIOT,gebart/RIOT,benoit-canet/RIOT,jferreir/RIOT,RubikonAlpha/RIOT,RubikonAlpha/RIOT,immesys/RiSyn,kushalsingh007/RIOT,jremmert-phytec-iot/RIOT,asanka-code/RIOT,automote/RIOT,smlng/RIOT,malosek/RIOT,automote/RIOT,ThanhVic/RIOT,kb2ma/RIOT,Josar/RIOT,hamilton-mote/RIOT-OS,kerneltask/RIOT,brettswann/RIOT,robixnai/RIOT,phiros/RIOT,robixnai/RIOT,dhruvvyas90/RIOT,adrianghc/RIOT,OlegHahm/RIOT,rousselk/RIOT,brettswann/RIOT,stevenj/RIOT,jremmert-phytec-iot/RIOT,rakendrathapa/RIOT,msolters/RIOT,dailab/RIOT,beurdouche/RIOT,kaleb-himes/RIOT,bartfaizoltan/RIOT,stevenj/RIOT,wentaoshang/RIOT,sumanpanchal/RIOT,jasonatran/RIOT,lazytech-org/RIOT,watr-li/RIOT,ThanhVic/RIOT,MonsterCode8000/RIOT,Hyungsin/RIOT-OS,jasonatran/RIOT,biboc/RIOT,herrfz/RIOT,zhuoshuguo/RIOT,JensErdmann/RIOT,biboc/RIOT,mtausig/RIOT,sumanpanchal/RIOT,zhuoshuguo/RIOT,herrfz/RIOT,stevenj/RIOT,stevenj/RIOT,jremmert-phytec-iot/RIOT,ant9000/RIOT,kbumsik/RIOT,altairpearl/RIOT,msolters/RIOT,ntrtrung/RIOT,jasonatran/RIOT,mziegert/RIOT,benoit-canet/RIOT,alex1818/RIOT,yogo1212/RIOT,phiros/RIOT,dkm/RIOT,OTAkeys/RIOT,authmillenon/RIOT,cladmi/RIOT,jhollister/RIOT,syin2/RIOT,Lotterleben/RIOT,JensErdmann/RIOT,Darredevil/RIOT,l3nko/RIOT,miri64/RIOT,Lexandro92/RIOT-CoAP,ntrtrung/RIOT,neiljay/RIOT,d00616/RIOT,msolters/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,rajma996/RIOT,arvindpdmn/RIOT,A-Paul/RIOT,lebrush/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,herrfz/RIOT,Ell-i/RIOT,abp719/RIOT,locicontrols/RIOT,robixnai/RIOT,MarkXYang/RIOT,RBartz/RIOT,OlegHahm/RIOT,rfswarm2/RIOT,mziegert/RIOT,asanka-code/RIOT,rajma996/RIOT,Yonezawa-T2/RIOT,avmelnikoff/RIOT,beurdouche/RIOT,x3ro/RIOT,RubikonAlpha/RIOT,MohmadAyman/RIOT,sgso/RIOT,luciotorre/RIOT,avmelnikoff/RIOT,TobiasFredersdorf/RIOT,marcosalm/RIOT,khhhh/RIOT,tfar/RIOT,luciotorre/RIOT,ThanhVic/RIOT,changbiao/RIOT,sumanpanchal/RIOT,openkosmosorg/RIOT,FrancescoErmini/RIOT,locicontrols/RIOT,rousselk/RIOT,jbeyerstedt/RIOT-OTA-update,DipSwitch/RIOT,Lotterleben/RIOT,DipSwitch/RIOT,BytesGalore/RIOT,AnonMall/RIOT,binarylemon/RIOT,d00616/RIOT,katezilla/RIOT,MarkXYang/RIOT,kushalsingh007/RIOT,zhuoshuguo/RIOT,DipSwitch/RIOT,LudwigOrtmann/RIOT,khhhh/RIOT,abkam07/RIOT,neumodisch/RIOT,kaspar030/RIOT,sumanpanchal/RIOT,rajma996/RIOT,LudwigKnuepfer/RIOT,bartfaizoltan/RIOT,jferreir/RIOT,Lotterleben/RIOT,RBartz/RIOT,thiagohd/RIOT,roberthartung/RIOT,fnack/RIOT,arvindpdmn/RIOT,Ell-i/RIOT,watr-li/RIOT,ant9000/RIOT,miri64/RIOT,josephnoir/RIOT,mfrey/RIOT,FrancescoErmini/RIOT,ximus/RIOT,l3nko/RIOT,daniel-k/RIOT,BytesGalore/PetersRIOT,centurysys/RIOT,EmuxEvans/RIOT,backenklee/RIOT,Yonezawa-T2/RIOT,latsku/RIOT,kYc0o/RIOT,PSHIVANI/Riot-Code,patkan/RIOT,ros2/ros2_embedded_riot,stevenj/RIOT,haoyangyu/RIOT,mfrey/RIOT,kushalsingh007/RIOT,herrfz/RIOT-old,marcosalm/RIOT,mfrey/RIOT,centurysys/RIOT,kaspar030/RIOT,roberthartung/RIOT,lazytech-org/RIOT,EmuxEvans/RIOT,miri64/RIOT,TobiasFredersdorf/RIOT,watr-li/RIOT,khhhh/RIOT,yogo1212/RIOT,latsku/RIOT,Ell-i/RIOT,l3nko/RIOT,RubikonAlpha/RIOT,PSHIVANI/Riot-Code,AnonMall/RIOT,Ell-i/RIOT,rousselk/RIOT,mtausig/RIOT,kYc0o/RIOT,ntrtrung/RIOT,chris-wood/RIOT,koenning/RIOT,marcosalm/RIOT,automote/RIOT,toonst/RIOT,MonsterCode8000/RIOT,kaspar030/RIOT,RubikonAlpha/RIOT,chris-wood/RIOT,josephnoir/RIOT,RBartz/RIOT,rfuentess/RIOT,Josar/RIOT,fnack/RIOT,Josar/RIOT,LudwigOrtmann/RIOT,alex1818/RIOT,immesys/RiSyn,BytesGalore/PetersRIOT,jhollister/RIOT,mziegert/RIOT,RIOT-OS/RIOT,haoyangyu/RIOT,chris-wood/RIOT,Lotterleben/RIOT,cladmi/RIOT,d00616/RIOT,luciotorre/RIOT,haoyangyu/RIOT,tdautc19841202/RIOT,rfswarm2/RIOT,kaspar030/RIOT,BytesGalore/PetersRIOT,jhollister/RIOT,gbarnett/RIOT,EmuxEvans/RIOT,khhhh/RIOT,hamilton-mote/RIOT-OS,fnack/RIOT,binarylemon/RIOT,plushvoxel/RIOT,haoyangyu/RIOT,Hyungsin/RIOT-OS,neiljay/RIOT,abp719/RIOT,avmelnikoff/RIOT,ant9000/RIOT,watr-li/RIOT,herrfz/RIOT-old,katezilla/RIOT,1blankz7/RIOT,zhuoshuguo/RIOT,Yonezawa-T2/RIOT,A-Paul/RIOT,adjih/RIOT,koenning/RIOT,yogo1212/RIOT,Osblouf/RIOT,toonst/RIOT,Hyungsin/RIOT-OS,RIOT-OS/RIOT,roberthartung/RIOT,dkm/RIOT,jferreir/RIOT,Lexandro92/RIOT-CoAP,phiros/RIOT,miri64/RIOT,A-Paul/RIOT,nsol-nmsu/RIOT,basilfx/RIOT,emmanuelsearch/RIOT,ntrtrung/RIOT,rajma996/RIOT,mziegert/RIOT,tdautc19841202/RIOT,kYc0o/RIOT,nsol-nmsu/RIOT,emmanuelsearch/RIOT,MohmadAyman/RIOT,ximus/RIOT,kaleb-himes/RIOT,AnonMall/RIOT,alignan/RIOT,x3ro/RIOT,tfar/RIOT,msolters/RIOT,ros2/ros2_embedded_riot,openkosmosorg/RIOT,josephnoir/RIOT,plushvoxel/RIOT,rfuentess/RIOT,gebart/RIOT,MarkXYang/RIOT,Josar/RIOT,cladmi/RIOT,brettswann/RIOT,backenklee/RIOT,plushvoxel/RIOT,MohmadAyman/RIOT,patkan/RIOT,binarylemon/RIOT,robixnai/RIOT,gautric/RIOT,kb2ma/RIOT,marcosalm/RIOT,rfuentess/RIOT,altairpearl/RIOT,daniel-k/RIOT,Lexandro92/RIOT-CoAP,authmillenon/RIOT,dailab/RIOT,kbumsik/RIOT,BytesGalore/PetersRIOT,RIOT-OS/RIOT,JensErdmann/RIOT,openkosmosorg/RIOT,kaleb-himes/RIOT,jhollister/RIOT,rousselk/RIOT,jhollister/RIOT,adjih/RIOT,watr-li/RIOT,adjih/RIOT,emmanuelsearch/RIOT,ks156/RIOT,kYc0o/RIOT,attdona/RIOT,changbiao/RIOT,BytesGalore/PetersRIOT,wentaoshang/RIOT,LudwigKnuepfer/RIOT,katezilla/RIOT,gebart/RIOT,malosek/RIOT,JensErdmann/RIOT,tfar/RIOT,RBartz/RIOT,Hyungsin/RIOT-OS,RubikonAlpha/RIOT,benoit-canet/RIOT,alignan/RIOT,khhhh/RIOT,latsku/RIOT,LudwigOrtmann/RIOT,RIOT-OS/RIOT,gautric/RIOT,BytesGalore/RIOT,ThanhVic/RIOT,latsku/RIOT,backenklee/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,TobiasFredersdorf/RIOT,attdona/RIOT,abp719/RIOT,asanka-code/RIOT,kb2ma/RIOT,arvindpdmn/RIOT,PSHIVANI/Riot-Code,ximus/RIOT,backenklee/RIOT,BytesGalore/RIOT,lebrush/RIOT,josephnoir/RIOT,mziegert/RIOT,beurdouche/RIOT,sgso/RIOT,biboc/RIOT,shady33/RIOT,ros2/ros2_embedded_riot,lazytech-org/RIOT,katezilla/RIOT,kushalsingh007/RIOT,binarylemon/RIOT,automote/RIOT,kb2ma/RIOT,MonsterCode8000/RIOT,jbeyerstedt/RIOT-OTA-update,jbeyerstedt/RIOT-OTA-update,shady33/RIOT,authmillenon/RIOT,watr-li/RIOT,benoit-canet/RIOT,nsol-nmsu/RIOT,RBartz/RIOT,dhruvvyas90/RIOT,RIOT-OS/RIOT,mfrey/RIOT,basilfx/RIOT,Lotterleben/RIOT,beurdouche/RIOT,RBartz/RIOT,herrfz/RIOT-old,abp719/RIOT,AnonMall/RIOT,sumanpanchal/RIOT,kbumsik/RIOT,Lexandro92/RIOT-CoAP,brettswann/RIOT,Yonezawa-T2/RIOT,wentaoshang/RIOT,attdona/RIOT,rousselk/RIOT,basilfx/RIOT,daniel-k/RIOT,FrancescoErmini/RIOT,openkosmosorg/RIOT,tdautc19841202/RIOT,cladmi/RIOT,stevenj/RIOT,foss-for-synopsys-dwc-arc-processors/RIOT,shady33/RIOT,patkan/RIOT,changbiao/RIOT,thomaseichinger/RIOT,ntrtrung/RIOT,malosek/RIOT,gbarnett/RIOT,MohmadAyman/RIOT,tdautc19841202/RIOT,adrianghc/RIOT,locicontrols/RIOT,robixnai/RIOT,LudwigOrtmann/RIOT,koenning/RIOT,adjih/RIOT,jfischer-phytec-iot/RIOT,tdautc19841202/RIOT,lebrush/RIOT,authmillenon/RIOT,syin2/RIOT,MonsterCode8000/RIOT,ros2/ros2_embedded_riot,BytesGalore/RIOT,OTAkeys/RIOT,dailab/RIOT,FrancescoErmini/RIOT,aeneby/RIOT,hamilton-mote/RIOT-OS,thomaseichinger/RIOT,neumodisch/RIOT,fnack/RIOT,centurysys/RIOT,rfswarm/RIOT,kbumsik/RIOT,phiros/RIOT,openkosmosorg/RIOT,herrfz/RIOT-old,TobiasFredersdorf/RIOT,rajma996/RIOT,dhruvvyas90/RIOT,immesys/RiSyn,rakendrathapa/RIOT,OTAkeys/RIOT,thiagohd/RIOT,Darredevil/RIOT,MarkXYang/RIOT,jremmert-phytec-iot/RIOT,yogo1212/RIOT,chris-wood/RIOT,mfrey/RIOT,neumodisch/RIOT,PSHIVANI/Riot-Code,hamilton-mote/RIOT-OS,1blankz7/RIOT,herrfz/RIOT,PSHIVANI/Riot-Code,haoyangyu/RIOT,Darredevil/RIOT,herrfz/RIOT-old,asanka-code/RIOT,brettswann/RIOT,fnack/RIOT,tfar/RIOT,jbeyerstedt/RIOT-OTA-update,DipSwitch/RIOT,aeneby/RIOT,A-Paul/RIOT,LudwigKnuepfer/RIOT,jferreir/RIOT,kerneltask/RIOT,neiljay/RIOT,neumodisch/RIOT,MonsterCode8000/RIOT,dkm/RIOT,sgso/RIOT,phiros/RIOT,automote/RIOT,ThanhVic/RIOT,BytesGalore/RIOT,kaspar030/RIOT,gbarnett/RIOT,khhhh/RIOT,ximus/RIOT,rajma996/RIOT,patkan/RIOT,jasonatran/RIOT,rfuentess/RIOT,emmanuelsearch/RIOT,locicontrols/RIOT,l3nko/RIOT,rfswarm/RIOT,thomaseichinger/RIOT,lazytech-org/RIOT,thomaseichinger/RIOT,authmillenon/RIOT,smlng/RIOT,ximus/RIOT,attdona/RIOT,JensErdmann/RIOT,latsku/RIOT,kerneltask/RIOT,Yonezawa-T2/RIOT,benoit-canet/RIOT,OlegHahm/RIOT,Lotterleben/RIOT,ximus/RIOT,neiljay/RIOT,toonst/RIOT,Ell-i/RIOT,cladmi/RIOT,latsku/RIOT,locicontrols/RIOT,rfuentess/RIOT,ks156/RIOT,neumodisch/RIOT,kerneltask/RIOT,jfischer-phytec-iot/RIOT,plushvoxel/RIOT,hamilton-mote/RIOT-OS